Land surface burst

Detonations which produce particle populations of the first category are land surface bursts, land subsurface bursts, vented underground bursts, and tower bursts. 

Land Surface Burst. The particle population clearly consists of two distinct components—crystalline particles and glass particles. The crystalline particles are local soil material which entered the fireball at a late time and hence were not melted. 

Land Subsurface Burst. Everything which was said above about land surface burst applies exactly to the aerial cloud particle population produced by a land subsurface burst in which an aboveground fireball appears. However, a third component of the particle population is found. This component appears to result from soil material which interacted with the fireball at high temperature but which was separated from the fireball early, before the temperature had fallen below the melting point of the soil materials. The particles in this component have diameters ranging from tens of microns to several centimeters and have densities which are apt to be quite low compared with those of the original soil components. The relative abundance of radionuclides in this component is quite constant from sample to sample and is independent of particle size. If we indicate by subscript 1 this third component and by 2,3 the aerial cloud components, radionuclide partitioning can be described by a series of equations of the forms... 

Tower Burst. If the energy of the detonation is sufficient to vaporize the entire tower mass, the particle population is like that described for the land surface burst. If, however, the entire tower is not vaporized, the particle population will consist of three identifiable components— the crystalline and glass components of the surface detonation plus a metal sphere population which arises from melted (not vaporized) tower materials resolidifying as spheres. Such spheres are metallic rather than metal oxide and exhibit the density and magnetic properties of the tower material. The size range of the spherical component is from a few microns to perhaps a few hundred microns diameter. If we indicate by... 

The following discussion gives an example of the data treatment required to characterize the population for three cases—a land surface burst, a land subsurface detonation, and an airburst detonation. These three examples cover the complete range of types of solutions to the characterization problem. 

Table III. Parameters of Distribution Functions (Land Surface Burst)...

As in the case of the land surface burst, complete characterization of the particle population requires only that particle mass, a volatile species, and a refractory species distribution with particle size be determined. All other isotopic distributions may be deduced from the istotope partition calculations described above. In the subsurface detonation, the earliest aerial cloud sample was obtained in the cloud 15 minutes after detonation. The early sample was, therefore, completely representative of the aerial cloud particle population. In Figure 5 the results of the size analysis on a weight basis are shown. Included for comparison is a size distribution for the early, local fallout material. The local fallout population and the aerial cloud population are separated completely from the time of their formation. 

In discussing the fission-product composition of fallout samples it is advantageous to choose some fission product as a reference nuclide, j, and express the composition of the other fission products i by a set of fij ratios. For local fallout from land-surface bursts the choice of 95Zr as reference nuclide has proved convenient. A ratio of particular interest is 7 89,95 since 89Sr and 95Zr generally fractionate from each other about as severely as any pair of nuclides. Thus, r89,95 indicates approximately the maximum extent of fractionation that will be observed in the sample. 

The character of the radioactive debris from a land surface explosion is determined largely by the extent of mixing between the extraneous debris injected into the cloud and the fission product radioactivities. Within the early cloud there is a well developed toroidal circulation (5), which is clearly evident in the case of air bursts and large yield surface bursts. In low yield surface explosions it may be obscured quickly by the dirt cloud and by rapid damping of a systematic circulation. 

B. Surface Burst. A surface burst weapon is detonated on or slightly above the surface of the earth so that the fireball actually touches the land or water surface. The area affected by blast, thermal radiation, and initial nuclear radiation will be less extensive than for an air burst of similar yield, except in the region of ground zero where destruction is concentrated. In contrast with airbursts, local fallout can be a hazard over a much larger downwind area than that which is affected by blast and thermal radiation. 

C. Subsurface Burst. A subsurface burst weapon is detonated beneath the surface of land or water. Cratering will generally result from an underground burst, just as for a surface burst. If the burst does not penetrate the surface, the only other hazard will be from ground or water shock. If the burst is shallow enough to penetrate the surface, blast, thermal, and initial nuclear radiation effects will be present, but will be less than for a surface burst of comparable yield. Local fallout will be very heavy if penetration occurs. 

Cyclic salts Salt ions that undergo rapid cycling between the ocean, atmosphere and land. This cycle involves ejection into the atmosphere via bursting bubbles and return via either dry deposition onto the sea surface or onto land followed by runoff back into the ocean. 

Accidental Release (Low Altitude, Hard Surface) (206) Muzzle Impact Safety (Projectile) (207) Impact Safe Distance (Projectile) (208) Missile Pull Off from Aircraft on Arrested Landing) (209) Time-to-Air Burst (211) Field Parachute Drop (212) and Air Delivery, Simulated (Parachute Drop) (T213) Class 300. Explosive Component Output Measurement by Steel Dent) (301.1) Detonator Output Measurement by Lead Disc (302) and Explosive Component Output Measurement by Aluminum Dent (303)... 

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